The present invention relates to a removable cartridge for the inked ribbon for typewriters, calculating machines or other office machines, comprising a container and two ribbon-carrying spools rotatable therein in either direction, the container having at least one main wall to which the axes of both spools are perpendicular, a series of side walls perpendicular to the main wall and a pair of slits in one of the side walls for the passage of the inked ribbon from the one to the other of the spools along a path which, between the slits, lies outside the container.
Cartridges for an inked ribbon are known which are provided with a closed container, in which the ribbon-carrying spools rotate in both directions under the action of a reversal mechanism. The reversal mechanism of the machine is provided with a pair of sensing elements fulcrumed internally on the entrainment pins for the spools. Each sensing element is thrust from the inside against the ribbon coils wound on to the spool, through an aperture in the pin and an aperture in the core of the spool. The sensing elements then control the reversal of the movement of the ribbon, when the number of coils of wound ribbon on a spool is no longer sufficient to hold the sensing element in. The use of sensor elements of this type, however, makes the reversal mechanism for the ribbon rather complicated and costly to realise.
Also known are typewriters which are provided with a reversal mechanism for the movement of the ribbon controlled by a sensor element which rests from the outside on the ribbon coils of the feed spool or of the take-up spool. The sensor element thus tests the quantity of wound ribbon, ordering the reversal when this quantity is less than a pre-established minimum number of coils, or else when it is greater than a maximum number of coils which is likewise pre-established. This reversal mechanism is very simple and therefore economical, but requires, for the replacement of a used ribbon, that the sensor element be pulled away from the relative spool, so as to allow the spool to be pulled off its pin. It is therefore not possible to use ribbon-carrying cartridges of known type, which have closed containers that do not allow the use of sensor elements which test externally the quantity of ribbon wound on the spools.